Just before noon on January 28, 1986, people watched with excitement as the space shuttle Challenger lifted off from its Florida launch pad -- but that excitement and hope soon turned into horror.

Just seventy-three seconds after liftoff, Challenger exploded, killing all seven astronauts on board.

One of its crew members was Christa McAuliffe, a school teacher from New Hampshire who had won a national competition to become the first teacher in space.

The goal was to boost interest in space exploration among American school children, many of whom were watching the Challenger's launch live on television or in person.

"We were all outside and the kids were all standing around and all of sudden we saw the smoke break into the Y shape," said Kari Anna Roy, who was in fourth grade at an elementary school in Lutz, Fla. "The teachers immediately knew something was wrong and rushed us back inside."

Roy said it took a while for her and her fellow classmates to grasp what happened.

"There was a teacher on board and we had been very excited about it and talking about it in school for a long time," she said. "It was a pretty devastating kind of thing especially for a school and we had all directly seen it happen right there."

Kevin Baron, now a reporter for Stars and Stripes, said that his Orlando elementary school watched every shuttle launch.

"We were in the lunchroom when the principal came in to tell us to turn on all the TVs," Baron said. "We walked outside into the field and the smoke trail was still coming down. We spent the rest of the day in school watching TV."

Jen Vargas also watched the launch from her Orlando elementary school.

"It was right before lunch, we were standing out there watching the shuttle go up. Usually it just goes straight up and it kind of veered off to the right. A lot of kids were confused, I was confused," she said. "We were crying and upset because we knew we had just seen the astronauts walk out and wave into the crowd and everything, and then we see them go up and the explosion happened.

The Challenger Disaster, 25 Years Later

The horrifying image of that massive fireball in the sky was replayed endlessly on television and burned into Americans' memories.

President Ronald Reagan was scheduled to deliver his State of the Union Address that night, but the White House postponed the speech and instead the president tried to comfort a grieving nation.

"We will never forget them, nor the last time we saw them, this morning, as they prepared for their journey and waved goodbye and ``slipped the surly bonds of earth'' to ``touch the face of God," Reagan said in what was perhaps the most memorable speech of his presidency.

Reagan also spoke directly to the nation's school children.

"I know it is hard to understand, but sometimes painful things like this happen. It's all part of the process of exploration and discovery. It's all part of taking a chance and expanding man's horizons," he said. "The future doesn't belong to the fainthearted; it belongs to the brave. The Challenger crew was pulling us into the future, and we'll continue to follow them."

The Challenger explosion not only dealt a major blow to the nation's psyche, but also to NASA. The shuttle program was grounded for nearly three years in the wake of the disaster as NASA investigated its cause. Ultimately, the investigation proved that the disaster could have been prevented.